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Unmanned Spaceflight.com _ Opportunity _ The Dark Dunes Of Erebus
Posted by: Nirgal Oct 11 2005, 09:28 PM
I've always been fascinated by the dark dune fields of Mars, resembling
in color the sands of, for example, the "black beaches" of Hawai
(inidcating the volcanic/basaltic origin ...)
Here is a colorized view of The dark Dunes of Erebus, as seen by Opporty on Sol 608 (click on image for full resolution (900 KB))
http://mitglied.lycos.de/user73289/misc/oppy_p18216a.jpg
Posted by: ddeerrff Oct 11 2005, 09:50 PM
Oil sands 
Posted by: avkillick Oct 11 2005, 10:52 PM
lol - if we did discover oil on Mars - expect a 1000x increase in funding...
Posted by: Bill Harris Oct 12 2005, 01:17 AM
Wonderful image, Nirgal.
I'm looking forward to examining the so-called "Elephant Dune" on the left side of the image. Those dunes are a redder color than the basalt-hematite sands of the ripples and I've seen a couple of instances where light-colored piece of evaporite is high in the dune. I'd suspect these are related to the ejecta blanket of Erebus.
--Bill
Posted by: Joffan Oct 12 2005, 05:15 AM
Well done - you really did make me laugh out loud for this post.. so true.
Posted by: CosmicRocker Oct 12 2005, 05:25 AM
These dunes/drifts/ripples really are beautiful, and Nirgal's colorized snapshot was quite evocative. Now that we are seeing them 'in person,' it is much easier to interpret the orbital images.
The white patch on top of the large drift has caught my attention, too. I would like to imagine it is the tip of a taller outcrop surrounded by recent sediments. But we really haven't seen prior evidence of outcrops that tall. I am still trying to convince myself that evidence of the ancient ejecta blanket exists, and has not been eroded off. Some parts of the surface look a bit jumbled, while other outcrops display bedding that is mostly contiguous between the blocks.
This is fun. And then there are those circular features that have become common. We need to map them.
Posted by: Bill Harris Oct 12 2005, 06:51 AM
I've seen no remnants of an ejecta blanket, either. Erebus is an ancient and highly eroded crater and we're seeing the bottom of the crater bowl. Although we see tilted strata in places, for the most part it is meridiani-flat. There are many little pieces of a puzzle that are starting to come together.
Glad to see you back, CR.
--Bill
Posted by: Tesheiner Oct 12 2005, 10:05 AM
The white patch on top of the large drift has caught my attention, too. I would like to imagine it is the tip of a taller outcrop surrounded by recent sediments. But we really haven't seen prior evidence of outcrops that tall. I am still trying to convince myself that evidence of the ancient ejecta blanket exists, and has not been eroded off. Some parts of the surface look a bit jumbled, while other outcrops display bedding that is mostly contiguous between the blocks.
This is fun. And then there are those circular features that have become common. We need to map them.
Isn't that white patch actually an outcrop on Erebus west side seen behind the dune/ripple?
Posted by: Bill Harris Oct 12 2005, 02:46 PM
We'll see better when we get closer, but I do believe that the white patch is on the crest of the dune. Here is a 5x exaggeration of the most recent Pancam image: the white patch is on the third dune back and looks to me to be in front of the Erebus rim outcrop.
There is another "white patch" on a ripple to the south that Oppy imaged a few Sols ago. Let me go through my archives tonight and I'll post another image.
--Bill
PS-- the earlier image is 1P180568717EFF60UPP2379L2M1. Evaporite boulder on the ripple crest at the crater edge.
Posted by: Tesheiner Oct 13 2005, 12:50 PM
I think you are right.
I checked it again, both left and right eye images, and there is no apparent difference in parallax between the dune and the white feature i.e. they are at the same distance.
Posted by: Tesheiner Oct 18 2005, 08:16 AM
That white patch can be clearly seen on sol 616 images.
http://nasa.exploratorium.edu/mars/opportunity/pancam/2005-10-18/1P182877345EFF62OUP2399L2M1.JPG
Posted by: Bill Harris Oct 18 2005, 12:55 PM
Yes, this entire area we are approaching is interesting. Not only are we encountering the largest dunes yet, they also have pieces of the evaporite rock high up in the dunes, and the Four Lane, where it meets the dune, appears to contain in-place ledges of a dark-colored rock. (EDIT: well, a rubble-pile of darker rock that is different than what we've seen)
This is the Four Lane two Pancam frames to the right of the image you presented, and I've added a 5x-vertical exaggeration view.
I hope Oppy spends some time looking around here.
--Bill
Posted by: atomoid Oct 18 2005, 09:28 PM
http://nasa.exploratorium.edu/mars/opportunity/pancam/2005-10-18/1P182877345EFF62OUP2399L2M1.JPG
I think its most likely to be the eroded bedrock dust (not any sort of outcrop) that collects at the top of this area due to the terrain features of the dune that make it probably in this area (itsa as if theres a little bowl or saddle feature up on that dune conjunction).
Remember, at eagle crater there similarly was this white dust collected in the ripples of the little dinner plate sized crater at the foot of the lander offramp.
which is apparently a rare occurrence, otherwise the white dust just blows away and we get cleaned dunes, but you can also see a lesser amount of dust in that earlier image of this similarly saddle-shaped area on the foreground dune http://mitglied.lycos.de/user73289/misc/oppy_p18216a.jpg
Posted by: Bill Harris Oct 22 2005, 01:34 PM
To add to my post of 18 Oct, here is a color image of the "rubble-pile of darker rock that is different" with a vertical exaggeration of 5x. It was taken on or about Sol 617-618.
A closer look at the rubble pile left me underwhelmed, and Oppy is back to dune-surfing. D:
--Bill
Posted by: ljk4-1 Mar 8 2006, 09:42 PM
Dune-tastic (Released 06 March 2006)
http://www.msss.com/mars_images/moc/2006/03/06
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